Observational evidence of equatorial ionospheric response to severe cyclonic storms ‘AILA’ and ‘WARD’ observed over the North Indian Ocean

Abstract

This work addresses the vertical atmosphere –ionosphere coupling through two cyclonic events AILA (23–26 May 2009) and ‘WARD’ (10–16 December 2009) observed over the North Indian Ocean. Combined ground Digisonde Tirunelveli (8.7oN, 77.8oE) observation, ECMWF reanalysis, and NOAA Outgoing Longwave Radiation data used to reveal the connection between atmosphere –ionosphere system. At the time of tropical cyclone, we observed a decrease in surface pressure and an increase of sustained oceanic winds. Thereby increases the tropical convection observed from the lowered OLR (Outgoing Longwave Radiation). The existence of Gravity wave oscillations of period ~4 h at the stratosphere and ionosphere regions indicate the propagation of low-frequency GWs (Gravity Waves) from the lower atmosphere. Weak eastward stratospheric winds observed at the time of onset of the cyclonic storm in both AILA and WARD events. The Ionospheric parameter foF2 and h’F2 show strong modulation at the time of cyclones AILA and WARD.